This invention relates to a resin composition which is excellent in moldability and heat resistance and hence suited for use in encapsulating a semiconductor device, and to a resin-encapsulated semiconductor device which is sealed with the resin composition.
With the current trend to further increasing the integration of semiconductor elements, the miniaturization of various function units of the elements and the enlargement of the elements per se are rapidly progressing now. For the purpose of sealing such semiconductor element with a resin composition, an epoxy resin composition comprising a thermosetting epoxy resin as a main component and a phenol resin as a curing agent has been extensively employed.
For example, a gate array of so-called ASIC (Application Specific IC) or a surface mount type package represented by a standard cell type LSI has been produced by making use of the aforementioned epoxy resin composition as a sealing resin. In the process of mounting these semiconductor devices on a substrate, various processes such as a vapor phase reflow, an infra-violet ray reflow and a solder dipping have been adopted. In this mounting process, the package is exposed to a high temperature in the order of 215 to 260.degree. C., so that a trace of water which has been penetrated into the package is suddenly vaporized, thus often giving rise to the generation of a crack in the sealing resin.
When the crack is extended to the external surface of the sealing resin, the moisture resistance reliability of resin-encapsulated semiconductor device will be damaged raising a serious problem. Moreover, when a crack is generated in the sealing resin, the resin will be caused to swell resulting in the deformation of the package, thus possibly making it difficult to mount the package on a substrate.
Furthermore, when such a package is mounted on a substrate, various problems including a cracking may be brought about even in the interior of the semiconductor element sealed with a resin. For example, PSG (phosphosilicate glass) or SiN (silicon nitride) which is used as a passivation film for a metallic interconnecting wiring layer formed of aluminum for example may be cracked, or the breakage of a gold bonding wire may be caused.
To solve these problems, there have been various demands as described below in the manufacture of a resin-encapsulated semiconductor device in particular of large size, these demands being mainly related to the sealing resin.
(1) The stress to be laid upon inner devices by the sealing resin should be minimized, and the adhesion between the sealing resin and a lead frame or a film such as PSG film, SiN film or polyimide film which is formed on a semiconductor element should be improved.
(2) The sealing resin should be excellent in heat resistance, i.e., sufficiently high in high temperature strength or in high temperature strength under moisture absorption so as to enable it to withstand the mounting temperature of the package. At the same time, the hygroscopicity of the sealing resin should be as low as possible.
On the other hand, in order to minimize the mounting area of a semiconductor chip in view of the popularization of a notebook type personal computer and a potable telephone, a flip chip mounting which enables a bare chip to be directly adhered onto a substrate has been widely adopted. In order to perform this flip chip mounting, a liquid sealing resin which is excellent in reliability, i.e. low in hygroscopicity and excellent in adhesivity is required to be employed.
In view of these demands, there has been developed a method of using a resin composition containing a silicone oil, the addition of which is intended to minimize the stress to be laid upon inner devices by the sealing resin and to improve the adhesion between the sealing resin and a lead frame, etc. However, the addition of silicone oil is accompanied with the problems that the silicone may oozed out to the surface of the molded product, thereby making the product defective in outer appearance or soiling a metal mold.
The conventional epoxy resin composition generally contains an acid anhydride or an amine compound as a curing agent. However, the resin composition containing such a curing agent is high in hygroscopicity, thus making it difficult to obtain a sealing resin having a highly reliable moisture resistance.
As explained above, a resin composition which is not only provided with every kinds of features demanded when it is to be used as a sealing resin, but also capable of exhibiting a low water absorption and avoiding the soiling of a metal mold is not yet available up to date.